Charles e



SORIBN'ER. MULTIPLE SWITGHBOARD SYSTEM.

(No Model.)

No; 487,096. Patented NOV. 29, 189 2.

UNITED STATES PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY, OF SAME PLACE.

MULTIPLE-SWITCHBOARD SYSTEM.

SPECIFICATION forming part of Letters Patent No. 487,096, dated November29, 1892.

Application filed March 6, 1892- To (ZZZ whom, it may concern:

Be it known that 1, CHARLES E. SCRIBNER, a citizen of the United States,residing at Chicago, in the county of Cook and State of lilinois, haveinvented a certain new and useful Improvement in Multiple-SwitchboardSystems, (Case No. 277,) of whichthe following is a full, clear,concise, and exact description, reference being had to the accompanyingdraw- IO ing, forming a part of this specification.

My invention relates to multiple-switchboard systems. Its objects are toprovide a switchboard system in which few contacts are included in theline-circuit and a suitable test 1 system therefor. I-Ieretofore,commonly, the

- circuit from a sub-station has been completed at the exchange throughthe contact-points of a series of spring-jacks, one upon each board,

thence through an individual annunciator,

and returning to the sub-station. WVhen a connection was made to theline by inserting a connecting-plug into a spring-jack, thecontact-points of the spring-jack were separated,

thus interrupting the circuit of the annunci- 2 5 ator and completingthe line-circuit through the contact-pieces of the connecting-plug andits connection, leaving, however, the contactpoints of a number of thespring-jacks still in the line-circuit. My invention is designed toavoid the inclusion of contact-points in the 1ine-circuit. I accomplishthis end by employing spring-jacks, one foreach circuit, upon eachswitchboard, each having a line-spring connected to one side of thecircuit or line, a

3 5 test ring or frame connected to the other line and an auxiliaryspring normally resting against a contact-anvil, all the said auxiliarysprings and anvils being connected in series in a branch circuit joiningthe two lines at 0 the exchange and including the annunciator.

Thus the complete circuit from the sub-station when not in use includesall the auxiliary springs and contacts and the annunciator, while thetalking-circuit includes only the 5 line-wires and the contacts of theplugs with the jack.

To establish connection with a line, I employ a connectingplug ofpeculiar construction. It is provided with an insulated conducting-coreadapted to make contact with the "line-spring, a second insulatedconduct- Serial No. 423,916. (No model.)

ing-sleeve concentric with the first, adapted to make contact with thetest-ring of the jack, and a spherical insulating-tip adapted to enterunder the auxiliary spring and raise it form its con tact'anvil when theplug is inserted into the jack.

The testing apparatus consists of a branch connectionjoiningthedifferent contact-pieces of a connecting-plug, including abattery and a telephone-receiver or other responsive device. When anoperator desires to test to determine Whether a connection alreadyexists to a line at some other board, she thrusts the plug alreadydescribed into the spring-jack of that line of her board. If the line benot in use, when the plug has been inserted to such a distance that theline-spring makes contact with the corresponding contact-piece of theplug a circuit will be completed from the bat- 7o tery through thetest-ring of the jack tested, the series of auxiliary springs and theircontacts, and the annunciator to the line-spring of the jack tested,thence returning to the battery. The completion of this circuit willproduce one click in the telephone of the operator testing. Then thefarther insertion of the plug into the jack causes the auxiliary springto be raised, thus breaking the circuit and producing a second click inthe telephone. If, however, the line be already in use, the circuit ofthe test-battery will not be completed at any time, since it is open atthe auxiliary spring of the jack at which connection already exists.That sleeve or contact-piece of 8 5 the plug which makes contact withthe linespring is preferably constructed of smaller diameter than thatof the test-ring, so that the two contact-pieces of the plug may notmake contact with the test-ring as the plug 0 is inserted into the jack.

My invention is illustrated in the accompanying drawing. Therein I haveshown a multiple-switchboard system comprising apparatus arranged inaccordance with my in- 5 vention and two sub-stations connected by linesto the exchange. The apparatus at the sub-station is all of the usualcharacter and need not be described. 7 Upon the switchboards are shownthe spring-jacks described. Each consists, as appears at a of alinespring 0, a test-ring c, and an auxiliary spring nd and firstboards, respectively, and to answering-jack 19 The return is throughconductor b resistance b and earth to station. A branch similar to thattraced before joins lines I) and b through the auxiliary springs andcontacts of jacks b b b and annunciator b Connection between two linesis eifected by means of connecting -plugs 01 d. The plug d at the firstboard is shown in longitudinal section, disclosing its construction. Itconsists of a central conducting-core e and a conducting-sleeve c,concentric with the core and insulated therefrom, and a sphericalinsulated tip 6 The sleeve 6 is adapted to make contact with a test-ringof a jack and the core 6 with the line-spring. The contactpoint of thecore is of less diameter than the sleeve, as described, in order toavoid making contact with the test-rings as the plug is inserted intothe jack. The tip 6 serves to raise the auxiliary spring a and isconstructed of such proportion that it shall not raise the auxiliaryspring until the piece 0 has made contact with the line-spring of thejack. Corresponding contact-pieces of the plugs 01 d are electricallyconnected together, the cores through a condenser f and the sleevesdirectly. The contact-points of the two callingkeys g h, of usualconstruction, are included in the conductors joining plugs d 61, wherebywhen either key is depressed both contaotpieces of one plug aredisconnected from those of the other and are connected to the two polesof a calling-generator 7;. Branch connections extend from the sameconductors to the contacts of a listening-key is, which is adapted toconnect the terminals of the operators telephone set Z and test-batterym to the extremities of the branches when the key is depressed. Otherbranches extend to the terminals of a clearing-out annunciator a in theusual manner. Circuit to sub-station 1 being in its normal condition,suppose that the subscriber at that station sends a callsignal to theexchange. The current finds circuit over line a through the auxiliarysprings and contacts and the annunciator a, returning byline a Theshutter of annunciator a is thrown down, notifying the operator that aconnection is desired. She inserts plug (1 in answering-jack a at herboard and de presses key 70, thereby looping her telephone into thecircuit to sub-station 1. Having learned the ordersay for a connectionwith station 2she at once inserts plug d into jack 1) of that line ather board. If the line be not in use, when the line-spring 0 makescontact with the contact-piece e the circuit of battery m is completedthrough the piece 6, spring 0, conductor 6, thence through the auxiliarysprings and contacts of the jacks b b b and the annunciator b totest-ring c, thence to the other contact-piece of plug d and to battery,and a click or other characteristic signal is produced in the telephonem. Then as the plug 01' is farther inserted into the spring-jack theauxiliary spring 0 is raised from its contact-anvil by the tip e,breaking the circuit just formed and causing another sound in telephonem. Obviously if the circuit to station 2 had been in use thetest-circuit just traced would have been already opened at thespring-jack at which the prior connection existed and no sound would beproduced in telephone m. Thus the occurrence to two responses intelephone m as she inserts plug d into the j ack. of a line calledindicates to the operator that the line is not in use, while the absenceof any sound indicates that it is busy. When the plug 01' is in place injack .1), the circuit between the two subscribers includes only thelines, the contacts of the spring-jack with the contract-pieces of theplugs, and the conductors joining the two plugs. It will beobserved thatthe circuits of the annunciators of both lines so connected are open.When conversation is finished, either subscriber may send a clearing-outsignal, to which neither of the individual annunciators can respond, butwhich will operate the clearing-out an nunciator n, thus notifying theoperator that she may disconnect the lines.

Obviously any other responsive device might be used in place of or inaddition to telephone m to give a visible or an audible signal.

Having thus described my invention, I

claim as new and desire to secure by Letters Patent- 1. A connecting-plug consisting of a central conducting-core, a conducting-sleeveconcentric with and insulated from said core and of such length as toleave a portion of said core exposed, and an insulated tip secured tosaid core, substantially as described.

2. The combination, with a spring-jack having a line-spring and a testring or frame insulated therefrom and an auxiliary springandcontact-anvil insulated from both linesprings and test-rings, of a plughaving one contactpiece making contact with the test-ring and anothercontact-piece making contact with the line-spring and an insulated tipentering under one end of the auxiliary spring and raising it from acontact-anvil, substantially as described.

IOCI

3. The combination, with a telephone-line extending from a sub-station,of spring-jacks at a central-station, each consisting of a linespring, atest-ring insulated therefrom, and auxiliary springs and contactanvils,as described, said line-springs and test-rings being connected with thetwo sides of line, respect ively, and a conductor joining the two sides,including in series an annunciator and all the auxiliary springs andcontacts, substantially as specified.

4. The combination, with a line-circuit extending from a sub-station toswitchboards at acentral station and connected at each board to aspring-jack having a test-ring, a linespring insulated therefrom, and anauxiliary spring and contact, said line-springs and testrings beingconnected to the sides of line, respectively, and said auxiliary springsand contacts being normally included in series with an annunciator in abranch connection goes 7 a between the two sides, of a plug insertedinto one jack, having contact-pieces making contact with the test-ringand the line-spring of the jack, respectively, and a tip separating theauxiliary spring from its anvil, and a testbattery and responsive deviceincluded in a circuit between the two contact-pieces of the plug,substantially as described.

In witness whereof I hereunto subscribe my name this 12th day ofFebruary, A. D. 1892.

CHARLES E. SORIBNER.

Witnesses:

M. J. TALLETT, GEORGE L. CRAGG.

